The Holladay 2 formula is conceptually based on the Holladay 1 formula; however it uses seven parameters for predicting the surgeon factor. These are the AL, corneal power, ACD, lens thickness, age, white-to-white corneal diameter and pre-operative refraction data. How the formula works in detail has not yet been revealed by Jack Holladay.
Parameters used for ELP prediction
These are AL, corneal power, ACD, lens thickness (optional), age (optional), white to-white corneal diameter (optional), pre-operative refraction data (optional).
Recommended eye type
The Holladay 2 formula is recommended for short – long* eyes.20
*W-K adjustment has been shown to extend the usage from "short – normal eyes" to "short – long eyes" for meniscus IOLs designs in the low plus to minus power range.24